The present invention concerns seating units having a reclineable back, and more particularly concerns seating units having a reclineable back and a forwardly movable/tiltable seat that moves with a synchronous movement as the back is reclined.
Manufacturers are becoming increasingly aware that adequate lumbar support is important to prevent lower back discomfort and distress in workers who are seated for long periods. A problem is that the spinal shape and body shape of workers vary tremendously, such that it is not possible to satisfy all workers with the same shape. Further, the desired level of firmness or force of support in the lumbar area is different for each person and may vary as a seated user performs different tasks and/or reclines in the chair and/or becomes fatigued. In fact, a static lumbar support is undesirable. Instead, it is desirable to provide different lumbar shapes and levels of support over a work day. Merely providing a particular shape or an adjustable lumbar support is not enough since seated users are constantly changing their position in the chair. Instead, the chair back must move and flex in a sympathetic manner that mirrors the movement of a human spine and lower back while providing good postural support in all body positions. Accordingly, an adjustable lumbar system is desired that is constructed to widely vary the shape and force of lumbar support. At the same time, the adjustable lumbar system must be simple and easy to operate, easily reached while seated, mechanically non-complex and low cost, and aesthetically/visually pleasing. Preferably, adjustment of the shape and/or force in the lumbar area should not result in wrinkles in the fabric of the chair, nor unacceptable loose/saggy patches in the fabric, even while the range of shape and force adjustment is increased.
A synchrotilt chair is described in U.S. Pat. No. 5,050,931 (to Knoblock) having a base assembly with a control, a reclineable back pivoted to the control, and a seat operably mounted to the back and control for synchronous motion as the back is reclined. This prior art chair incorporates a semi-rigid flexible shell that, in combination with the chair support structure, provides a highly-controlled postural support during the body movements associated with tasks/work (e.g., when the back is in an upright position) and during the body movements associated with recline/relaxation (e.g., when the chair is in a reclined position). This prior art chair moves a seated user""s upper body away from the user""s work surface as the user reclines, thus providing the user with more area to stretch. In fact, moving around in a chair and not staying in a single static position is important to good back health in workers whose jobs require a lot of sitting. However, users often want to remain close to their work surface and want to continue to work at the work surface, even while reclining and relaxing their body and while having continued good postural support.
Modern customers and chair purchasers also demand a wide variety of chair options and features, and a number of options and features are often designed into chair seats. However, improvement in seats is desired so that a seated user""s weight is adequately supported on the chair seat, but simultaneously so that the thigh area of a seated user is comfortably, adjustably supported in a manner that adequately allows for major differences in the shape and size of a seated user""s buttocks and thighs. Additionally, it is important that such options and features be incorporated into the chair construction in a way that minimizes the number of parts and maximizes the use of common parts among different options, maximizes efficiencies of manufacturing and assembling, maximizes ease of adjustment and the logicalness of adjustment control positioning, and yet that results in a visually pleasing design.
Accordingly, a chair construction solving the aforementioned problems is desired.
In another aspect on the present invention, a back construction for a seating unit includes a back frame, and a compliant back having a forwardly-protruding lumbar support section that is characteristically flexible and bendable, such that the compliant back can be flexed to a plurality of different convex shapes. Top and bottom connections pivotally connect the compliant back to the back frame. An adjustable force-generating mechanism is operably attached to at least one of the compliant back and the back frame. The force-generating mechanism is constructed to provide an adjustable biasing force that adjustably biases the lumbar support section forwardly for optimal lumbar support for a seated user""s back, but the force-generating mechanism characteristically provides the biasing force without forcing a shape change in the compliant back.
In another aspect on the present invention, a seating unit including a base assembly having a control housing having an energy source therein, and a back assembly movably supported on the base assembly. The base assembly includes a back support operably interconnected to the energy source. The back support includes a back frame and a back shell connected to the back frame by at least one connection. The back shell includes a resiliently flexible polymeric sheet adapted to support a back of a seated user. The sheet includes a lower area disposed generally in a pelvic area on the seating unit, a central area disposed above the lower area and generally in a lumbar area on the seating unit, and an upper area disposed above the central area and generally in a thoracic area on the seating unit. A cushion is provided on a forward face of the back shell. A vertically adjustable lumbar support is located in front of the back shell. The lumbar support is movably supported on the back support and configured for vertical adjustment to change a shape of a front surface of the back in the lumbar area. The vertically adjustable lumbar support includes laterally extending handles constructed to engage and follow configured non-parallel opposing perimeter edges of the back shell and constructed to slidably engage the vertically adjustable lumbar support to permit the handles to adjust laterally in and out to follow the perimeter edges.
These and other features and advantages of the present invention will be further understood and appreciated by those skilled in the art by reference to the following specification, claims, and appended drawings.